The present invention relates to metal-oxide-semiconductor field-effect transistors (MOSFET), and more specifically, to silicon germanium (SiGe) and germanium (Ge) material layers.
The MOSFET is a transistor used for switching electronic signals. The MOSFET has a source, a drain, and a metal oxide gate electrode. The metal gate is electrically insulated from the main semiconductor n-channel or p-channel by a thin layer of insulating material, for example, silicon dioxide or high dielectric constant (high-k) dielectrics, which makes the input resistance of the MOSFET relatively high. The gate voltage controls whether the path from drain to source is an open circuit (“off”) or a resistive path (“on”).
N-type field effect transistors (NFET) and p-type field effect transistors (PFET) are two types of complementary MOSFETs. The NFET uses electrons as the current carriers and with n-doped source and drain junctions. The PFET uses holes as the current carriers and with p-doped source and drain junctions.
Using high percentage SiGe or germanium layers as enabling elements in MOSFET devices may improve performance. To work with current complementary metal oxide semiconductor (CMOS) devices, the SiGe and germanium layers may be disposed on a silicon (Si) substrate.